About this course
Taxonomy is the branch of biology that classifies all living things. It was developed by the Swedish botanist Carolus Linnaeus, who lived during the 18th Century, and his system of classification is still used today. Linnaeus invented binomial nomenclature, the system of giving each type of organism a genus and species name. He also developed a classification system called the taxonomic hierarchy, which today has eight ranks from general to specific: domain, kingdom, phylum, class, order, family, genus, and species.
The basic taxonomic ranks, in order from most general to most specific, are:
Domain: The broadest classification. There are three main domains:
- Bacteria: Single-celled organisms without a nucleus.
- Archaea: Single-celled organisms similar to bacteria but with unique biochemical characteristics.
- Eukarya: Organisms with complex cells containing a nucleus, including plants, animals, fungi, and protists.
Kingdom: The second rank, which divides organisms into major groups. For example, animals are classified under the kingdom Animalia, while plants fall under Plantae.
Phylum: A group of organisms that share a major body plan or structural feature. For example, the phylum Chordata includes all animals with a spinal cord, such as mammals, birds, and fish.
Class: A subdivision of phylum. For example, within the phylum Chordata, the class Mammalia includes all mammals.
Order: Groups within a class. For instance, the order Carnivora includes animals like dogs, cats, and bears.
Family: A grouping of related genera. For example, the family Felidae includes all cats, from lions to domestic cats.
Genus: A group of closely related species. For example, the genus Panthera includes lions, tigers, leopards, and jaguars.
Species: The most specific classification, referring to a group of individuals capable of interbreeding and producing fertile offspring. For example, the species Panthera leo refers to lions.
